1. Field of the Invention
The present invention generally relates to an optical system, a color information displaying method, and an image projection displaying apparatus using an optical deflecting array in which a plurality of optical deflecting devices is arrayed in two dimensions, each capable of changing a direction of outgoing light with respect to incoming light, and an optical deflecting device capable of changing the direction of outgoing light with respect to incoming light, and more particularly to a technology preferable to an image apparatus such as a projector, or a rear projection television.
2. Description of the Related Art
Japanese Laid-open Patent Application No. 2004-78136 discloses an optical deflecting device for deflecting incoming light to multiple predetermined directions, an optical deflecting array including a plurality of the optical deflecting devices in an one dimension or two dimensions, and an image projection displaying apparatus using the optical deflecting array.
As the above-described optical deflecting device, there is an optical deflecting device capable of optically deflecting the incoming light to two directions with respect to one axis set as a center, an optical deflecting device capable of optically deflecting the incoming light to multiple directions with respect to two or more axes set as centers, and a like.
The above-described optical deflecting array is used as an optical system of an image projection displaying apparatus. If the image projection displaying apparatus conducts a single color display, the optical deflecting array can be configured by the optical deflecting array using optical deflecting devices having a single axis. However, in order to display a color image, it is required to combine three primary colors. Accordingly, in the optical system disclosed in the Japanese Laid-open Patent Application No. 2004-78136, a color wheel configured by color filters of the three primary colors is placed on a light path between a color light source and the optical deflecting device, and is rotated, so that the color display is conducted by rapidly switching a color of the incoming light.
FIG. 1 is a diagram showing a color image projection displaying apparatus 100 (Related Art 1). In FIG. 1, the color image projection displaying apparatus 100 includes a white color light source 101, a color wheel 102 being a rotating disc shape, a rod lens 103, an optical deflecting array 104 deflecting to two directions with respect to a single axis, a projection lens 105, and a light absorption plate 106. The color image projection displaying apparatus 100 projects an image onto a screen 107.
It is assumed that a light flux output from the white color light source 101 passes through any one of filters, for example, a red filter within the color wheel 102 switching filters in a time sequence. The light flux becomes a red color light (R) and passes through the rod lens 103. The rod lens 103 makes the light flux be a parallel light, and the light flux enters individual optical deflecting devices of the optical deflecting array 104. In this case, color information corresponding to a red image is input to the individual optical deflecting devices of the optical deflecting array 104. In a case of a presence of the color information, an incident red color light (R) is lead to the projection lens 105. On the other hand, in a case of an absence of the color information, the incident red color light (R) is lead to the light absorption plate 106. This switch of the deflecting direction is conducted by displacing a member as a mirror. In the following, one operation leading the light flux to the projection lens 105 in the case of the presence of the color information is called an ON operation, and another operation leading the light flux to the light absorption plate 106 in the case of the absence of the color information is called an OFF operation.
At the ON operation, an image shown on the optical deflecting array 104 is output to the projection lens 105, and is formed on the screen 107. At the OFF operation, the image is output to a direction to which the image is not output to the projection lens 105, and is absorbed by the light absorption plate 106, so that the image does not reach the screen 107. In a case in that the three primary colors are projected onto the screen 107 in the time sequence at high speed, human eyes do not recognize an individual image in which a color is decomposed into the three primary colors because of a residual image, and see an image combining three primary colors as a color image.
Japanese Laid-open Patent Application No. 2004-138881 discloses an optical system for displaying a color image by a single optical deflecting device alone. An image projection displaying apparatus (Related Art 2) using the above-described optical system distributes a single incoming light flux to four directions: three directions respective to the three primary colors, and one direction for the OFF (black) information, by using an optical deflecting device using a two-axis deflection. After that, the image projection displaying apparatus forms an image onto a screen by combining reflected light in three directions respective to the three primary colors.
FIG. 2A is a side view of an optical system in the Related Art 2. FIG. 2B is a perspective view showing a state of light fluxes output from a light source. In FIG. 2A and FIG. 2B, an optical deflecting array 10, a first field lens 11, projection lenses 12R, 12G, and 12B, a second field lens 13, an image displaying part (screen) 14, a light source 15, a light flux shaping lens 16, a plane reflection mirror 17, a light flux L, and an optical axis O for the entire optical system are shown. In addition, R, G, B, and off are affixed to reference signs, and denote color information of each of the primary colors (red, green, blue) and the OFF information. In FIG. 2A, in order to avoid an intricate drawing, an light source system for inputting a parallel light flux into the optical deflecting array is omitted. In addition, in FIG. 2B, light fluxes are shown until a surface 11a of the first field lens 11, and the light fluxes after passing the surface 11a are omitted.
The incoming light flux is output from the light source 15 shown in FIG. 2B, becomes the parallel light flux L by the light flux shaping lens 16 which is generally called a condensing lens, changes a direction at the plane reflection mirror 17, and then enters the optical deflecting array 10 along the optical axis O perpendicularly set to a surface of the optical deflecting array 10. It should be noted that a light flux is shaped by a light shielding mask 16a so that a shape of a cross section of the light flux L is approximately the same as and slightly larger than a shape of an available portion of the optical deflecting array 10.
The light flux L entering to the optical deflecting array 10 is deflected in response to the color information, and reflected light becomes a light flux LR for a given time. When the light flux LR enters the surface 11a of the first field lens 11, the light flux LR is refracted and output from the optical deflecting array 10 so that a center light of the light flux LR is parallel to the optical axis O. Moreover, the light flux LR is set to be adjacent to the first field lens 11. An optical axis of the light flux LR is affected by an image-forming action while passing the projection lens 12R parallel to a normal line with respect to the surface of the optical deflecting array 10, and the light flux LR enters the second field lens 13 having approximately the same size as the first field lens 11. By the second field lens 13, the light flux LR is refracted so that center light of the light flux LR directs toward a display center 14A of the image displaying part 14. Accordingly, the light flux LR forms an image at the image displaying part 14. It should be noted that even if the light flux LR includes color information, the image cannot be a color image as long as light emitted from a white color source is used. Thus, in the Related Art 2, a color filter FR is arranged at an incoming side of the surface 11a of the first field lens 11.
For a next given time, the optical deflecting array 10 is deflected based on next color information. For example, the light flux L refracts at the optical deflecting array 10, and becomes a light flux LG. A center light of the light flux LG seems to be identical to the optical axis O in FIG. 2A. However, as seen from the perspective view shown in FIG. 2B, the center light of the light flux LG distances from the optical axis O similar to the light flux LG in a plan view. Accordingly, an action which the light flux LG is affected from the optical system is also the same as the light flux LR, except for a difference between a side view and a plan view. Thus, a center of the light flux LG positions to the display center 14a of the image displaying part 14, and the light flux LG forms an image.
Moreover, in a further time, a light flux LB is generated. In the same manner described above, a center of the light flux LB positions to the display center 14a of the image displaying part 14. In the above explanation, the light fluxes LR, LG, and LB include respective color information. In this case, as the color information, binary information showing a presence or an absence of a color is input. Accordingly, each of the light fluxes LR, LG, and LB includes a light beam acquired by a deflected direction when a color is present. In a case of information indicating that the color is not present, that is, in a case of the OFF information, a deflected direction by the optical deflecting device is shown as a direction of a light flux Loff in FIG. 2B. However, the deflected direction of the OFF information is identical to the three primary colors. Since the light flux Loff is an unnecessary light flux for the image display, the light flux Loff is shielded at a location ineffective to other available light fluxes, for example, on the incoming side of the surface 11a of the first field lens by a shielding member which is not shown.
However, as long as there is no image accumulation action at the image displaying part 14, an image by the light flux LR vanishes when an image of the light flux LR is displayed. In the same manner, when an image by the light flux LB is displayed, the image of the light flux LG vanishes. That is, since images corresponding to the three primary colors are displayed in a time sequence, there is no full-color image at any moment. However, these images can be seen by human eyes to be the full-color image of the residual image if a switch period is sufficiently shorter.
The Japanese Laid-open Patent Application No. 2004-138881 discloses an image projection displaying apparatus using another optical system and displaying a color image by a single optical deflecting device alone (Related Art 3).
In the Related Art 3, by using an optical deflecting device having a two-axis deflection, in contrary to FIG. 2A and FIG. 2B, incoming light fluxes of R, G, and B in respective three directions are directed to one direction leading to a projection lens and three directions for the OFF (black) information, reflected light in a single direction leading to the projection lens forms an image on a screen.
FIG. 3A is a perspective view showing a part of light source system for explaining the Related Art 3, and FIG. 3B is a side view of the light source system. In FIG. 3A and FIG. 3B, reference signs r, g, and b are affixed to other reference sign, similar to the reference sings R, G, and B, to individually indicate a color. In the Related Art 3, three separate light sources corresponding to three primary colors are used. In FIG. 3, for the sake of convenience, only one light source 15G of three light sources is shown.
At approximately the same position where the light flux LG in FIG. 2B enters to the first field lens 11a, a condenser lens 16G is placed in FIG. 3B. The light source 15G is arranged so that the light flux LG goes backward by the condenser lens 16G and a divergent light flux forms a luminous flux LG′. The luminous flux LG′ is a single color light of green of the three primary colors. A light source itself may emit a green color, or a color filter of green may be arranged to a white color light source.
In this configuration, in a case in that an optical deflecting device of an optical deflecting array is deflected to the same direction as the direction forming the light flux LG in FIG. 2B, in FIG. 3A, the luminous flux LG′ is deflected to be a light flux L′ perpendicular to a surface of an optical deflecting array 10. At the side view shown in FIG. 3B, since the luminous flux LG′ and the light flux L′ are overlapped with each other, the light source 15G is not shown. However, a light source 15R, the luminous flux LR′, and the light flux L′ are in the same relationship. The light flux L′ enters an opening 12a of a projection lens 12, an outgoing light of the light flux L′ is focused on a surface of an image displaying part 14 so that a light beam passing a center of the light flux becomes identical to a display center 14a of the image displaying part 14. Then, image including the color information of green indicated by the optical deflecting array 10 is displayed at the image displaying part 14. By the same configurations regarding other single colors of the primary colors, that is, red and blue, luminous fluxes LR′ and LB′ are deflected to be identical to the light flux L′ as a light flux including respective color information corresponding to the optical deflecting array 10. Accordingly, there is no difference at the image displaying part 14, and three color images are identically overlapped with each other. If all deflected direction of the optical deflecting array 10 are directed to a direction corresponding the color information of red, the luminous flux LR′ is deflected to a direction of the light flux L′. However, the luminous fluxes LG′ and LB′ are deflected to completely different directions.
The luminous flux LG′ will be described. A deflection surface of the optical deflecting device is plane mirror. A normal line N of the plane mirror of each optical deflecting device is directed toward in a direction dividing an inner angel between the incoming light flux and the outgoing light flux into two equal angels. The plane mirror reflects a light beam to a direction symmetric to the normal line N. However, in the above-described condition, the luminous flux LG′ becomes a reflected light flux symmetric to a normal line Nr, which will be described later, as indicated by a luminous flux LG′r shown in FIG. 3A. In FIG. 3A, it appears that the luminous flux LG′r overlaps with the light flux L′ since both fluxes LG′r and L′ are drawn in a plane. However, the luminous flux LG′r and the light flux L′ are emitted in different directions from the optical deflecting array 10. Since the optical deflecting array is an aggregate of the optical defecting devices, normal lines cannot be individually drawn clearly, only the normal line Nr is shown at a center of the optical deflecting array 10, representatively. In the following, only the normal line Nr is shown in the same manner. If the deflected direction of the optical deflecting array 10 is always directed to a direction corresponding the color information of blue, for the same reason, the luminous flux LG′ becomes a reflected light flux symmetric to the normal line Nb as indicated by the luminous flux LG′b in FIG. 3A. A light flux, which is unwanted for an image display, does not enter the projection lens and becomes a stray light. Accordingly, the light flux can be absorbed by using a light absorption plate, or a like. In a case of using the color information of each color, the optical deflecting device which the OFF information enters inclines a deflection surface toward in the same direction as a direction on which the light flux Loff is formed in FIG. 2B. In this case, a normal line of the plane mirror of the optical deflecting device is directed to a direction of the normal line Noff. Since the luminous flux LG′ becomes a light flux LG′ off by the optical deflecting device of the luminous flux LG′, and does not enter the projection lens, image pixels corresponding to the optical deflecting device of the luminous flux LG′ form a black display. In the above, the luminous flux LG′ is described. Other luminous fluxes are not shown other than the luminous flux LR′b in FIG. 3B but the same manner is conducted for each color. As shown in FIG. 3A, the luminous fluxes LG′b and LR′off overlap with each other at substantially the same light flux location. Thus, since each single color light source does not interfere with other colors, each color light source can successively emit light even if the color information of other colors are being displayed.
Next, an example case of an optical deflecting device capable of conducting two-axis light deflection as described in the above Japanese Laid-open Patent Application No. 2004-78136 and No. 2004-138881 will be described. FIG. 4A and FIG. 4B are diagrams showing a configuration of the optical deflecting devices.
FIG. 4A is a top view of the optical deflecting device. In FIG. 4A, a fulcrum member 403 and electrodes 405a through 405d are transparently shown. FIG. 4B is a cross-sectional view taken on line B-B′ of FIG. 4A. The optical deflecting device shown in FIG. 4A and FIG. 4B is shown as one optical deflecting device in a group of optical deflecting devices arranged in two dimensions as an optical deflecting array.
The optical deflecting device in FIG. 4A and FIG. 4B is one optical deflecting device in that a member including a light reflection area is displaced by an electrostatic attraction so that a light flux entering the light reflection area is deflected to a reflection direction being changed. The optical deflecting device includes a substrate 401, a plurality of controlled members 402, a fulcrum member 403, a plate member 404, and a plurality of electrodes 405a through 405d. Each of the plurality of controlled members 402 includes a stopper at an upper potion. The plurality of controlled members 402 are arranged at a plurality of edges of the substrate 401, respectively. The fulcrum member 403 includes a nib, and is arranged on an upper surface of the substrate 401. The plate member 404 does not includes a fixed end, includes the light reflection area on an upper surface, and includes a electric conductor layer formed by a member being electrically conductive partially at least. The plate member 404 is movably arranged in a space forming by the substrate 401, the fulcrum member 403, the stoppers of the plurality of controlled members 402. The plurality of electrodes 405a through 405d are respectively arranged on the substrate 401, and approximately face to the electric conductor layer of the plate member 404.
The above-described optical deflecting devices include the following advantages:                a tilt angle is determined by contacts of the fulcrum member 403, the substrate 401, and the plate member 404. Accordingly, a deflection angle of a mirror is easily and stably controlled.        the plate member having a thin film is reversed rapidly by applying a different electric potential to a facing electrode as a center of the fulcrum member 403. Accordingly, a response speed can be improved.        Since the plate member 404 does not have a fixed end, the plate member 404 is not deteriorated in along term without a deformation caused by a twist or a like, and is driven with a lower voltage.        Since a fine and light plane member can be formed by a semiconductor process, a shock from a collision to the stopper can be lower. Accordingly, the plane member 404 is not be deteriorated in a long term.        Each configuration of the controlled members 402, the plate member 404, and the light reflection area is arbitrarily determined. Therefore, an on/off ratio (S/N (Signal to Noise) ratio in an imaging device, or a contrast ratio in a picture reproducer) can be improved.        The semiconductor process and an apparatus thereof can be used. Accordingly, it is possible to be further miniaturization and integration at lower expense.        The plurality of electrodes 405a through 405d are arranged with a central focus on the fulcrum member 403. Accordingly, a deflection direction of one-axis two dimensions and a deflection direction of two-axis three dimension can be realized.        
Next, an example of a driving method of the above-described optical deflecting device will be described with reference to FIG. 5A and FIG. 5B, and FIG. 6. This driving method is a driving method (light deflection method) in a case in that a plate member 404 is electrically floating.
A state in which the plate member 404 shown in FIG. 4A and FIG. 4B will be described with reference to FIG. 5A and FIG. 5B. FIG. 5A shows cross-sectional views taken along a line A-A′ and a line C-C′ of FIG. 4A in an OFF operation, and FIG. 5B shows cross-sectional views taken along the line A-A′ and the line C-C′ of FIG. 4A in an ON operation.
In FIG. 5A and FIG. 5B, electric potentials for applying to the electrodes 404a through 404d are switched, and then an optical deflection operation is conducted. In addition, FIG. 5A and FIG. 5B show electrostatic attraction (black arrows) which occurs by the electric potentials applied to the electrodes 405a through 405d. FIG. 6 shows a timing chart of the electric potentials applied to the electrodes 405a through 405d. 
In the following, referring to FIG. 5A and FIG. 5B, and FIG. 6, a driving method of the optical deflecting device, and a inclination displacement operation (that is, optical deflection operation) of the plate member 404 will be described. First, in the OFF operation of FIG. 6, a higher electric potential a is applied to the electrode 405a, a lower electric potential c is applied to the electrode 405b, and a medial electric potential b is applied to the electrode 405c and the electrode 405d. Accordingly, the plate member 404, which includes the electric conductor layer, and is electrically floating and facing to the electrodes 405a through 405d, has the same electric potential as the medial electric potential b, which is analogized easily from a calculation of a simple closed circuit.
Thus, the electrostatic attraction does not occur with respect to the electrodes 405c and 405d at an ON side. On the other hand, as shown in FIG. 5A, the electrostatic attraction occurs with respect to the electrodes 405a and 405b at an OFF side, and the plate member 404 is inclined and displaced to the OFF side. This operation is not only for the OFF operation in a series of the optical deflection operation, but also for a reset operation conducted when the optical deflection operation is initialized.
In the ON operation in FIG. 6, the higher electric potential a is applied to the electrode 405c, the lower electric potential c is applied to the electrode 405d, and the medial electric potential b is applied to the electrode 405b. Accordingly, the plate member 404, which includes the electric conductor layer, and is electrically floating and facing to the electrodes 405a through 405d, has the same electric potential as the medial electric potential b, which is analogized easily from a calculation of a simple closed circuit. Thus, the electrostatic attraction does not occur with respect to the electrodes 405a and 405b at the OFF side. On the other hand, as shown in FIG. 5B, the electrostatic attraction occurs with respect to the electrodes 405c and 405d at the ON side, and the plate member 404 is inclined and displaced to the ON side.
In FIG. 4A and FIG. 4B, the plate member 404 of the optical deflecting device is shown as a single layer. However, the plate member 404 is not limited to be a single layer but may have two layers as described in the Japanese Laid-open Patent Application No. 2004-78136 and No. 2004-138881.
In addition, in FIG. 5A and FIG. 5B, and FIG. 6, the optical deflection operation of the one-axis two dimensions, in which a side of the electrodes 405a and 405b is the OFF side and a side of the electrode 405c and 405d is the ON side, is described. Since the fulcrum member 403 is arranged with a conical shape at a center of the optical deflecting device, the plate member 404 can be inclined to a side of the electrodes 405a and 405c and a side of the electrodes 405b and 405d, by arbitrarily changing a voltage to apply to the electrodes 405a through 405d. That is, the light deflection of the two-axis three dimension can be realized.
In addition, in FIG. 4A, FIG. 4B, FIG. 5A, FIG. 5B, and FIG. 6, the optical deflecting device has a configuration of displacing the plate member 404 electrically floating and applies the driving method. Alternatively, the optical deflecting device may be an optical deflecting device having a configuration and a driving method in that the plate member 404 is contacted and conductive to the fulcrum member 403, and an electric potential is given to the plate member. That is, the optical deflecting device can be a device capable of conducting a light deflection of two-axis three dimensions.
When a light is illuminated from an arbitrary direction to the plate member 404 having the light reflection area in the optical deflecting device described above, a reflection direction of light is deflected to one of four directions in response to an inclination direction of the plate member. Moreover, when light is entered from a direction perpendicular to a substrate surface (an array surface), reflected light is reflected to four directions being symmetric to each other in a case in that the incoming light is defined as a center. In the optical deflecting array, the optical deflecting devices are closely arranged lengthwise and crosswise, the number of the optical deflecting devices being arranged lengthwise and crosswise is determined based on the number of pixels lengthwise and crosswise necessary to the image display.
The image projection displaying apparatus as described as the Related Art 1 includes one optical deflecting array of the one-axis deflection, one white color light source, and one color wheel. In addition, in the image projection displaying apparatus, by configuring an optical lens, an optical system is included. In the Related Art 1, light from the white light source is successively switched to the three primary colors of R, G, and B using the color wheel to lead to the optical deflecting array. Thus, a time for displaying the color information of each color is divided into three. Accordingly, a light use effect is lowered in one frame time.
Moreover, since the color wheel is rotated at high speed, a noise occurs. In addition, it is required to operate each of the optical deflecting devices forming the optical deflecting array by synchronizing the color wheel being rotated at high speed. As a result, a process of image data becomes complicated.
Furthermore, a mixed color problem may occur at a boundary of color filters forming the color wheel. Thus, it is required to stop an operation of the optical deflecting device, and one frame time cannot be fully used for the image display. In addition, an expense using the color wheel is increased.
In the Related Art 1, in addition to the above-described problems, in general, there is a problem which is called a color flicker or a color breaking. Color flicker is a phenomenon in that light like a rainbow can be seen in a moment when human eyes see an image projected on a screen, and makes human eyes tired. This is a typical problem of the optical system using the color wheel to successively project colors individually.
That is, the primary colors of R, G, and B are successively displayed on the screen and are combined by the residual image. However, a color combination is different among individuals. In addition, when the human eyes move from an end to another end of the screen or when the human eyes blink, the human eyes cannot combine the primary colors well. As a result, color flicker occurs. Color flicker is a main problem in the optical system switching colors by using the color wheel.
In order to solve the problem of color flicker, it is considered that a color switch of the color wheel is conducted at higher speed. For example, in a case in that an image is displayed at 60 Hz of a frame rate, one frame time is 16.7 msec. When this frame time is divided into the three primary colors of R, G, and B, a display time for each color becomes 5.56 msec. In this case, the color wheel may be formed by six divisions of R, G, B, R, G, and B, and a rotation speed of the color wheel may be set to be three times faster. Accordingly, an every display time for each of colors may be reduced to be 0.93 msec. (in practice, an accumulated time can be recognized to be 5.56 msec for six repeats within one frame time). However, even if color flicker is slightly reduced by switching colors at higher speed, it is not sufficient to eliminate color flicker.
The image projection displaying apparatus as described as the Related Art 2 includes one optical deflecting array of the two-axis deflection, one white color source, and three color filters (R, G, and B). In addition, in the image projection displaying apparatus, by configuring an optical lens, an optical system is included. In the Related Art 2, white color light is entered from one direction to the optical deflection array of the two-axis deflection and reflected to four directions of R, G, B, and OFF (black). An outgoing light in a direction of each of the colors R, G, and B becomes respective color light by passing a respective color filter. Three colors are combined by a combination of a field lens, a projection lens, and then a field lens, and displayed on the screen.
However, in the Related Art 2, each of colors R, G, and B radiating in three directions is received by the field lens. Accordingly, a scale of a combination of the field lens, the projection lens, and the field lens becomes larger, and a length of a light path for combining the colors R, G, and B illuminated from the optical deflecting array becomes longer. As a result, the optical system becomes larger.
The image projection displaying apparatus of the Related Art 3 includes one optical deflecting array, a total three light sources corresponding to the colors R, G, and B. In addition, in the image projection displaying apparatus, by configuring an optical lens, an optical system is configured. In the Related Art 3, the three colors R, G, and B enter from relative three directions to the optical deflecting array of the two-deflection, and are reflected to four directions: an ON (for all R, G, and B) direction, an OFF (R) direction, an OFF (G) direction, and an OFF (B) direction. Light from the ON (for all R, G, and B) direction is lead to the projection lens, and is displayed on the screen. Since the light from the ON (for all R, G, and B) direction passes a light path shared with all colors R, G, and B, the three colors R, G, and B are naturally combined. However, in the Related Art 3, since three light sources are required, the image projection displaying apparatus costs more.